@Togodumnus - to your question: isn't the answer that clearly yes, BA think they can (ie tell the difference ... and have decided with that in mind that they will still go down the route of...).
Ok I'm being glib by saying that and I apologise for sounding so argumentative. I also don't quite believe it - I think that the truth is more a medium to long term issue in that they need a consistent (high) volume at the right (again high) level of quality, which thus justifies such an on-going recruitment scheme.
Truth be told I do have huge sympathy for those (including a number of good friends from training days) who are currently sitting there in limbo with the qual's but no job. There, but for the grace of God (and bag-fulls of luck during the competitive process), would I also sit.
A question I have asked of recruiters in other companies who have made (or in 1 case been about to make but didn't) a similar commitment and the answer was consistently the same, similarly to what we are hearing here, that "we cannot get the quantity of candidates we need at the required standard". Their answers, not mine (and no, of course I'm not going to name them).